Method and machine for manufacturing pieces made of ceramic or metallic material by the technique of additive manufacturing

ABSTRACT

The disclosed method includes selecting a suspension ceramic or metal photocurable composition (CPC or MPC); preparing a sacrificial organic material (SOM) forming a photocurable layer destroyed by heating; for manufacturing pieces, on the working tray, forming successive layers of SOM cured by irradiation, the one or more CPC or MPC-based pieces being manufactured by machining a recess in a layer of cured SOM; depositing the CPC or MPC within the recesses; curing the CPC or MPC to obtain a hard horizontal surface level with the adjacent layer of cured SOM, when forming each recess, it is delimited by previously defined patterns, the depth(s) selected in order to ensure the continuity of the one or more pieces to be manufactured; and obtaining one or more green pieces inserted in the SOM, which are subjected to debinding by heating in order to destroy the SOM in which they are trapped.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/999,028filed Aug. 20, 2018 which claims priority to FR Application No. 1770870filed Aug. 18, 2017. Each of the previously noted applications is herebyincorporated by reference in their entirety.

The present invention relates to a method and a machine for producinggreen pieces made of at least one material selected from the ceramicmaterials and the metallic materials using the technique of additiveprocesses, said green pieces being then subjected to debinding andsintering operations in order to obtain finished pieces.

BACKGROUND OF THE INVENTION

The technique of additive processes or additive manufacturing, alsodesignated by stereolithography, generally comprises the following stepsin order to obtain ceramic green pieces:

-   -   building, by computer-aided design, a computer model of the        piece to be manufactured, the sizes of the model being slightly        larger than those of the piece to be manufactured so as to        anticipate a shrinking of the ceramic material during the        manufacturing of the piece; and—manufacturing the piece by means        of the technique of additive manufacturing, consisting in:    -   forming, on a rigid support, a first layer of a photocurable        composition generally comprising at least one ceramic material,        at least one photocurable monomer and/or oligomer, at least one        photoinitiator and, when appropriate, at least one plasticizer        and/or at least one solvent and/or at least one dispersant;    -   curing the first layer of the photocurable composition by        irradiation (by laser scanning of the free surface of said layer        or by a diode projection system) according to a pattern defined        from the model for said layer, forming a first stage;    -   forming, on the first stage, a second layer of the photocurable        composition;    -   curing the second layer of the photocurable composition, by        irradiation according to a pattern defined for said layer,        forming a second stage, this irradiation being performed in the        same way as the first layer;    -   optionally, repeating the above mentioned steps until the green        piece is obtained.

Then, in order to obtain the finished piece, the green piece is cleanedin order to remove the non-cured composition; the cleaned green piece isdebinded; and the cleaned and debinded green piece is sintered in orderto obtain the finished piece.

The same operations are performed in the case of a metallic material.

The manufacturing of green pieces made of a ceramic material or ametallic material having particular shapes may present difficulties.

(1) Currently, once they are built, the pieces are located within anon-cured paste block, which requires to search for the solid piecewhich is located within a sticky paste, and then to wash the piece, forexample, by spraying it with a chemical product in order to remove thissticky paste.

(2) The pieces to be built may have at least one cantilevered part whichshould be supported during its building. Reference can be made to FIGS.1-3 of the appended drawing, which show a piece P to be manufactured forwhich, regardless of the orientation thereof, there will be always aface F which should be supported during the manufacturing thereof,otherwise the piece will collapse.

(3) The pieces to be manufactured may have passages p ofthree-dimensional geometry, as it is the case for the piece P of FIGS.1-3. This passage cannot be correctly cleaned as there is no toolsadapted to this geometry.

The Applicant Company searched for a solution to these problems andfound that the building of the piece inside a shell or hull made of asacrificial material—which is constituted only by the organic part of aceramic or metallic photocurable composition, allows :

-   -   to obtain, after the irradiation of each layer, a cured        sacrificial material block enclosing the piece being searched,        block which will be merely debinded in order to obtain the        piece; the cleaning of the piece is thus optimized as it is no        required anymore to search for the piece within the paste and to        clean the piece using a chemical product;    -   in the case of pieces having cantilevered faces and thus being        prone to collapse during their building, to ensure that the        shell or hull of cured sacrificial material favorably makes the        support being searched;    -   in the case of pieces having hollow parts or passages leading to        their surface and difficult, if not impossible, to be correctly        cleaned, to be able to release these spaces which are then        filled with sacrificial material, during the debinding in order        to obtain the desired hollow parts or passages without the need        for inserting a tool or a cleaning chemical product.

Furthermore, the invention offers the complementary advantage that theamount of material to be used for the shell or hull can be optimized byproviding the proper amount, without excess.

BRIEF SUMMARY OF THE INVENTION

Thus, the present invention first relates to a method for manufacturingat least one piece made of at least one material selected from theceramic materials and the metallic materials using the technique ofadditive manufacturing, said one or more pieces being formed in thegreen state, and then subjected to debinding and sintering operations,said method comprising the following steps:

-   -   (1) building, by computer-aided design, a computer model of the        piece to be manufactured or of the pieces to be simultaneously        manufactured;    -   (2) forming, on a working tray, said one or more pieces to be        manufactured, which are based on a ceramic or metallic        photocurable composition (CPC or MPC) comprising:    -   a mineral part consisting of at least one powdered ceramic        material or at least one powdered metallic material; and    -   an organic part able to be destroyed by heating during the        debinding, and comprising at least one photocurable monomer        and/or oligomer and at least one photoinitiator,

characterized by the fact that it comprises the following steps:

-   -   selecting a CPC or MPC having the consistency of a suspension        able to flow in order to form a layer;    -   preparing a sacrificial organic material (SOM) able to form a        photocurable layer and to be destroyed by heating during the        debinding, said SOM comprising at least one photocurable monomer        and/or oligomer and at least one photoinitiator;    -   for the building of said one or more pieces, on the working        tray, forming successive layers of SOM which are stacked on each        other, each layer of SOM being caused to cure by irradiation        before applying the next layer, the one or more properly        speaking pieces based on CPC or MPC being built by:    -   forming, by machining, at least one recess in at least one layer        of cured SOM from the upper surface thereof;    -   depositing, within said one or more recesses, the CPC or MPC in        order to fill the one or more recesses;    -   curing, by irradiation, the CPC or MPC located within said one        or more recesses in order to obtain a hard horizontal surface        having the same level as the adjacent layer of cured SOM,    -   wherein when forming each recess, the latter is delimited        according to the one or more patterns previously defined from        the computer model, and the depth(s) thereof selected in order        to ensure the continuity of the piece(s) to be manufactured, and    -   obtaining, once the cured layers are stacked, one or more green        pieces embedded in the SOM, such green pieces being subjected to        a debinding by heating in order to destroy the SOM in which it        is trapped or they are trapped, so as to release it or them and        then submit it or them to a sintering.

The ceramic materials are the powdered sinterable ceramic materialsselected in particular from alumina (Al₂O₃), zirconia (ZrO₂),zirconia-reinforced alumina, alumina-reinforced zirconia, zircon(ZrSiO₄), silica (SiO₂), hydroxyapatite, silica zircon (ZrSiO₄+SiO₂),silicon nitride, tricalcium phosphate (TCP), aluminum nitride, siliconcarbide, cordierite and mullite.

The metallic materials are the powdered sinterable metallic materialsselected in particular from pure metals, such as Al, Cu, Mg, Si, Ti, Zn,Sn, Ni . . . , their alloys, and the mixtures of pure metals and alloysthereof.

The recesses can have to be formed in the entire thickness of a curedlayer of SOM or with a height lower than the height of a layer. Theyalso can have to be formed with a height higher than the thickness of alayer, for example, with a height equal to the height of several layersbeing previously spread.

When the one or more pieces to be manufactured comprise hollow parts,the latter should lead to the outer surface of the piece so that the SOMcan be released during the debinding.

The method according to the invention can be applied to themanufacturing of several identical pieces, which will be trapped in asame block of SOM.

A pasty SOM can be used, which is spread in a layer by scraping, or asuspended SOM can be used, which is applied by dipping the tray in abath of said suspension in order to form, each time, the layer of SOM tobe cured, and scraping the layer thus formed.

In the case where the piece(s) to be manufactured comprise(s) at leastone lateral part which should be supported during the building,advantageously a computer model of the shape of the SOM in cured statewas built beforehand, by computer-aided design, this shape being suchthat the manufactured piece(s) is (are) supported during their building.

In order to form the recess(es), a mechanical machining can beperformed. A laser machining can also be performed, in particular underthe conditions of setting the laser power between 1 and 3 watts and thelaser displacement speed between 1 and 100 millimeters per second.

Also, at each machining step, it is possible to blow and suck thedebris, particularly at the same time as said machining is conducted.

The CPC or MPC can be applied within the one or more recesses by adispensing nozzle.

The curing by laser irradiation of each layer of SOM and the curing bylaser irradiation of the layers of CPC or MPC located within therecesses under the conditions of setting the laser power between 70 and700 milliwatts and a laser displacement speed between 1,000 and 6,000millimeters per second, can be conducted.

The debinding can be conducted at a temperature between 50 and 800° C.,especially between 100 and 700° C.

The present invention also relates to a machine for manufacturing atleast one piece made of at least one material selected from the ceramicmaterials and the metallic materials by the method using the techniqueof additive manufacturing such as defined above, characterized in thatit comprises:

-   -   a frame surrounding a working tray comprising a working surface;    -   irradiating means facing the working surface;    -   means for supplying and spreading into layers, on the working        tray, a sacrificial photocurable organic material (SOM);    -   machining means able to form at least one recess in a layer of        photocured SOM from the upper part thereof;    -   means for blowing and sucking the debris resulting from said        machining;    -   means for filling the one or more recesses formed in each layer        of photocured SOM in order to complete the layer thus recessed        by a ceramic or metallic photocurable composition (CPC or MPC)        able to flow;    -   irradiating means arranged above the working tray and able to        irradiate, in order to cure it, each layer of SOM once spread,        and irradiate, in order to cure it, the CPC or MPC once located        within the recesses made in the successive layers of cured SOM.

Such a machine, able to apply into layers a SOM under the form of apaste, can comprise a gantry having at least one scraping blade andbeing able to move on the frame above the working surface such that thefree edge of the scraping blade(s) is able to spread the layers of SOMpaste on the working surface, or the SOM being supplied by at least onedispensing nozzle movable in front of at least one scraping blade whichspreads the SOM into an uniform layer when passing thereon.

Such a machine, able to apply into layers a SOM under the form of asuspension, can comprise a tank to be filled with said suspension, inwhich the working tray is able to be lowered step by step in order toform thereon, at each step, a layer to be irradiated, as well as arecoater in order to ensure that the suspension is dispensed on theentire surface to be irradiated.

The means for supplying at least one CPC or MPC on the working surfacecan be constituted by at least one dispensing nozzle movable above acorresponding recess in order to apply the corresponding compositiontherein.

According to a first embodiment, the or at least one of the nozzles canbe supplied with SOM or CPC or MPC by a hose connected to a tank, inparticular a piston supply tank.

According to a second embodiment, the or at least one of the nozzles canbe supplied with SOM or CPC or MPC by a cartridge which forms the upperpart of it, which contains a stock of SOM or CPC or MPC and which isrefillable from a supply tank that can be mounted on the machine, orwhich when empty is replaceable by a full cartridge, wherein thisreplacement can be ensured by a robotic arm.

The or at least one of the nozzles can be movably mounted

-   -   using a robotic arm; or    -   on a gantry which has both a slide allowing to move it along the        horizontal axis x of the working tray and a slide allowing to        move it along the horizontal axis y of the working tray; or    -   on a gantry having at least one scraping blade in order to allow        the displacement thereof along the horizontal advance axis x of        the scraping blade, said gantry also comprising a slide allowing        to move it along the horizontal axis y.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better illustrate the subject-matter of the presentinvention, a particular embodiment of it will be described below, forindicative and non-limiting purposes, with reference to the appendeddrawings.

In the drawings:

FIG. 1 is a perspective schematic view of a piece to be manufactured,comprising a three-dimensional cylindrical passage;

FIGS. 2 and 3 are schematic views of the piece of FIG. 1 in yz and xzplanes, respectively;

FIG. 4 is a cross-sectional schematic view of the piece beingmanufactured according to the invention;

FIG. 5 shows schematic views of the piece manufactured according to theinvention before the debinding, in the zy and zx planes;

FIGS. 6 and 7 are perspective schematic views of the piece of FIG. 5before and after debinding, respectively;

FIGS. 8-11 illustrate the successive steps for forming a layer ofsacrificial photocurable material;

FIGS. 12 and 13 illustrate the formation of a layer constituted both bya sacrificial organic material and a photocurable ceramic material.

DETAILED DESCRIPTION OF THE INVENTION

When referring to FIGS. 4-6, it can be seen that the formation of apiece P according to the invention within a shell or hull S made ofcured sacrificial organic material is illustrated, the passage p beingalso filled with sacrificial organic material S.

When referring to FIG. 8, a machine 1 for manufacturing green pieces hasbeen schematically shown, comprising a device 2 for scraping a pastelayer on a working surface of a horizontal working tray 3.

The scraping device 2, slidably mounted on the frame 4 of the machine,comprises a gantry 5 carrying, at the front part thereof, a scrapingblade 6 having a horizontal scraping edge and which moves forwards whenreferring to FIG. 8, that is, along the horizontal axis x.

The front vertical wall of the gantry 5 has a horizontal slide 7 alongwhich two nozzles 8, 9 can move along the horizontal axis y,perpendicular to the axis x, one (8) for depositing a photocurablesacrificial organic material and the other (9) for depositing a ceramicphotocurable composition.

In FIG. 11, the galvanometric head 10, which directs the laser beam, isalso shown.

FIG. 8

A layer of sacrificial organic material 11 is deposited on the workingsurface of the working tray 3 by moving the scraping device 2 along theaxis x and the nozzle 8 along the axis y.

FIG. 9

By forward movement, the scraping device 2 has leveled the layer ofsacrificial organic material 11 by moving the blade 6.

FIG. 10

The scraping device 2 has been returned to the initial position thereofand raised.

FIG. 11

The layer 11 thus deposited is caused to polymerize by applying thelaser beam, the galvanometric head 10 being in use.

FIG. 12

A laser machining of the cured layer 11 is performed in order to formtherein a recess 12, this laser machining operation being performed byblowing and sucking the debris together with lasing.

FIG. 13

Using the second nozzle 9, a photocurable ceramic composition 13 hasbeen deposited within the recess, which composition is polymerized byapplying the laser beam (the galvanometric head 10 being in use).

The formation of a cured layer of sacrificial organic material andceramic material has been described, both being photocured.

The piece being searched is built layer after layer of photocuredsacrificial organic material, the recesses intended to be filled withphotocurable ceramic material being drilled in at least one layer ofpreviously-cured sacrificial organic material, the depths of therecesses and the locations thereof on the layers of sacrificial organicmaterial being selected in order to ensure the formation of the ceramicpiece being searched.

1. A machine for manufacturing at least one piece made of at least oneof ceramic materials and metallic materials, the machine comprising: aframe surrounding a working tray comprising a working surface;irradiating means facing the working surface; means for supplying andspreading into layers, on the working tray, a sacrificial photocurableorganic material (SOM); machining means able to form at least one recessin a layer of photocured SOM from the upper part thereof; means forblowing and sucking the debris resulting from said machining; means forfilling the one or more recesses formed in each layer of photocured SOMin order to complete the layer thus recessed by one of a ceramicphotocurable composition (CPC) and a metallic photocurable composition(MPC) able to flow; irradiating means arranged above the working trayand able to irradiate, for curing each layer of SOM once spread, andirradiate, for curing the CPC or MPC once located within the recessesmade in the successive layers of cured SOM.
 2. The machine according toclaim 1, further comprising: a gantry having at least one scraping bladeand being configured to move on the frame above the working surface suchthat the free edge of the one or more scraping blades is able to spreadthe layers of SOM paste on the working surface, or wherein the SOM issupplied by at least one dispensing nozzle movable in front of at leastone scraping blade which spreads the SOM into a uniform layer whenpassing thereon.
 3. The machine according to claim 1, furthercomprising: a tank to be filled with a SOM suspension, in which theworking tray is configured to be lowered step by step in order to formthereon, at each step, a layer to be irradiated, as well as a recoaterin order to ensure that the SOM suspension is dispensed on the entiresurface to be irradiated.
 4. The machine according to claim 1, whereinthe means for supplying at least one CPC or MPC on the working surfaceare constituted by at least one dispensing nozzle movable above acorresponding recess in order to apply the corresponding compositiontherein.
 5. The machine according to claim 2, wherein the at leastnozzle is supplied with one of SOM, CPC, or MPC by a hose connected to atank.
 6. The machine according to claim 2, wherein the at least onenozzle is supplied with one of SOM, CPC, or MPC by a cartridge whichforms the upper part of the nozzle, said cartridge containing a stock ofthe one of SOM, CPC, or MPC and being refillable from a supply tankmountable on the machine, or which when empty is replaceable by a fullcartridge, wherein this replacement can be ensured by a robotic arm. 7.The machine according to claim 2, wherein the at least one nozzle ismovably mounted by means of a robotic arm.
 8. The machine according toclaim 2, wherein the at least one nozzle is movably mounted on a gantrywhich has both a slide that moves the nozzle along the horizontal axis xof the working tray and a slide that moves the nozzle along thehorizontal axis y of the working tray.
 9. The machine according to claim2, wherein the at least one nozzle is movably mounted on a gantry havingat least one scraping blade that allows displacement thereof along thehorizontal axis x of the scraping blade, said gantry also comprising aslide allowing displacement along the horizontal axis y.
 10. The machineof claim 5, wherein the tank is a piston supply tank.